Pressure sensor comprising an elastic sensor layer with a microstructured surface

Abstract

Disclosed is a pressure sensor comprising sensor layers ( 12, 14 ) which are made of an elastic, resistive material and are applied to a polymer film that is not represented. ( 22 ) embodies a spacer that is coated with an adhesive. One sensor layer ( 14 ) is provided with a microstructured surface encompassing spherical structures ( 20 ) within an active zone ( 16 ). The compression path amounts to 10 micrometers at an extension R of the structures of 50 micrometers. The structures ( 20 ) are large compared with a certain surface roughness. The inventive pressure sensor is produced by injection molding, etching, embossing, or by of an electron beam technique or laser beam technique. Disclosed are variations thereof, which function differently.

1. Pressure sensor comprising:
 a first carrier foil with a first sensing layer; and 
 a second carrier foil with a second sensing layer, 
 the first and second carrier foils being arranged in such a way with respect to each other that the first and second sensing layers are facing each other, 
 wherein the first and second sensing layers are configured such that electrical resistance between two terminal contacts of the sensor depends on an area of contact between the two sensing layers, 
 wherein, in the region of an active zone of the pressure sensor, at least the second sensing layer has a microstructured surface with predefined structures formed of an elastic material, 
 wherein the first and second carrier foils are arranged in such a way with respect to each other that, if no force acts on the pressure sensor, the structures of the second sensing layer remain in contact with the first sensing layer and form the area of contact in conjunction said first sensing layer and 
 wherein the structures are compressed under influence of a force exerted on the pressure sensor so that an extent of the area of contact is increased. 
 
     
     
       2. Pressure sensor according to  claim 1 , wherein the first sensing layer comprises a first resistive material. 
     
     
       3. Pressure sensor according to  claim 2 , wherein the structures of the second sensing layer comprise a second resistive material. 
     
     
       4. Pressure sensor according to  claim 1 , wherein the structures of the second sensing layer comprise an insulating material and wherein at least one of the structures is coated at least in certain parts with a conductive material or a second resistive material. 
     
     
       5. Pressure sensor according to  claim 3 , wherein at least one of the structures is coated at least in certain parts with a conductive material. 
     
     
       6. Pressure sensor according to  claim 3 , wherein the second resistive material comprises a lower resistance than the first resistive material. 
     
     
       7. Pressure sensor according to  claim 1 , wherein the first sensing layer is contacted by the terminal contacts at two contact points located at a distance from each other. 
     
     
       8. Pressure sensor according to  claim 7 , wherein the two contact points are positioned opposite each other with respect to the active zone of the sensor. 
     
     
       9. Pressure sensor according to  claim 1 , wherein each of the first and second sensing layers is contacted on the side facing away from the other sensing layer in an extended area by one of the terminal contacts. 
     
     
       10. Pressure sensor according to  claim 1 , wherein each of the first and second sensing layers is contacted at a contact point by one of the terminal contacts and wherein both contact points are positioned opposite each other with respect to the active zone of the sensor. 
     
     
       11. Pressure sensor according to  claim 3  wherein at least one of the first and second resistive material comprises a conductive elastomer material. 
     
     
       12. Pressure sensor according to  claim 1 , wherein the structures of the microstructured surface are shaped such that they taper in the direction of the first sensing layer. 
     
     
       13. Pressure sensor according to  claim 1 , wherein the structures of the microstructured surface are produced by a process of injection moulding, etching, stamping, electron beam machining or laser beam machining. 
     
     
       14. Pressure sensor according to  claim 1 , wherein the first and second carrier foils are laminated together. 
     
     
       15. Pressure sensor comprising:
 a first carrier foil with a first sensing layer and 
 a second carrier foil with a second sensing layer, 
 wherein the first and second sensing layers are configured such that electrical resistance between two terminal contacts of the sensor depends on an area of contact between the two sensing layers, and 
 wherein, in a region of an active zone of the pressure sensor, at least the second sensing layer has a microstructured surface with predefined structures formed of an elastic material, 
 wherein the first and second carrier foils being arranged in such a way with respect to each other that the first and second sensing layers are facing each other and that, if no force acts on the pressure sensor, the structures of the second sensing layer remain in contact with the first sensing layer and form the area of contact in conjunction said first sensing layer; and 
 wherein, under influence of a force exerted on the pressure sensor, the structures are compressed so that an extent of the area of contact is increased. 
 
     
     
       16. Pressure sensor according to  claim 15 , wherein the first sensing layer comprises a first resistive material. 
     
     
       17. Pressure sensor according to  claim 16 , wherein the structures of the second sensing layer comprise a second resistive material. 
     
     
       18. Pressure sensor according to  claim 15 , wherein the structures of the second sensing layer comprise an insulating material and wherein at least one of the structures is coated at least in certain parts with a conductive material or a second resistive material. 
     
     
       19. Pressure sensor according to  claim 17 , wherein at least one of the structures is coated at least in certain parts with a conductive material. 
     
     
       20. Pressure sensor according to  claim 17 , wherein the second resistive material comprises a lower resistance than the first resistive material. 
     
     
       21. Pressure sensor according to  claim 15 , wherein the first sensing layer is contacted by the terminal contacts at two contact points located at a distance from each other. 
     
     
       22. Pressure sensor according to  claim 21 , wherein the two contact points are positioned opposite each other with respect to the active zone of the sensor. 
     
     
       23. Pressure sensor according to  claim 15 , wherein each of the first and second sensing layers is contacted on the side facing away from the other sensing layer in an extended area by one of the terminal contacts. 
     
     
       24. Pressure sensor according to  claim 15 , wherein each of the first and second sensing layers is contacted at a contact point by one of the terminal contacts and wherein both contact points are positioned opposite each other with respect to the active zone of the sensor. 
     
     
       25. Pressure sensor according to  claim 17 , wherein at least one of the first and second resistive material comprises a conductive elastomer material. 
     
     
       26. Pressure sensor according to  claim 15 , wherein the structures of the microstructured surface are shaped such that they taper in the direction of the first sensing layer. 
     
     
       27. Pressure sensor according to  claim 15 , wherein the structures of the microstructured surface are produced by a process of injection moulding, etching, stamping, electron beam machining or laser beam machining. 
     
     
       28. Pressure sensor according to  claim 15 , wherein the first and second carrier foils are laminated together.